The present invention relates to a wood preservative, particularly a wood attacking-, decaying- and staining-inhibitory composition. More particularly, to a wood attacking-, decaying- and staining-inhibitory composition against a wood damage by an insect which is harmful to wood such as termites and Lyctus brunneus Stephens which damage a building or a furniture made of wood and also by a wood decaying microorganism including a brown-rot fungus such as Fomitopsis palustris and a white-rot fungus such as Trametes versicolor and also against a dirt by a wood-staining fungus such as Aspergillus niger and Aureobasidium pullulans, as well as a method and use for producing the same.
Various known wood preservatives are employed in order to control insects harmful to wood, such as termites and Lyctus brunneus Stephens and also to prevent decaying by a wood-rot fungus such as Fomitopsis palustris and Coniophora puteana or a staining by a wood-staining fungus such as Aspergillus niger and Aureobasidium pullulans. However, any of such known wood preservatives badly affects the safety in humans and animals as well as the environment, and may destroy the ecosystem of nature.
An objective of the present invention is to provide a wood preservative which exhibits an excellent insect-controlling activity against a harmful insect as well as a high anti-decaying activity against a wood-rot fungus and a high antifungal activity against a fungal growing in wood and staining the wood.
Another objective of the invention is to provide a wood preservative that is highly safe to humans and animals and does not affect the environment adversely.
Still another objective of the invention is to provide a wood preservative capable of controlling an insect harmful to a wood, a wood-rot fungus and a wood-staining fungus reliably and efficiently.
In order to accomplish the objectives described above, the inventors have conducted extensive study to examine various material and compounds and have found that a Piper methysticum plant or a processed product thereof, or a chemical compound obtainable from the plant or derivatives thereof exhibit an excellent effect for preserving wood without any bad influence on mammals and environment.
Thus, the present invention is:
1. A wood preservative comprising as an active ingredient a Piper methysticum plant or a processed product thereof, or a compound represented by Formula (I): 
xe2x80x83wherein R1, R2, R3, R4 and R16 are same or different and each denotes a hydrogen atom, hydroxy or a C1-4 alkoxy, or R1 and R2 are taken together to form a group represented by xe2x80x94Oxe2x80x94(CH2)nxe2x80x94Oxe2x80x94 wherein n is an integer of 1 to 3, R5 is a C1-4 alkoxy and X is xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94CH2xe2x80x94CH2xe2x80x94 or epoxyethylene, and the bond:

xe2x80x83denotes a single bond or a double bond.
2. The wood preservative according to 1. which is an insect-controlling agent.
3. The wood preservative according to 1. which is an anti-decaying agent.
4. The wood preservative according to 1. which is an anti-fungal agent.
5. The wood preservative according to 1. which is a termite-controlling agent.
6. The wood preservative according to 1. wherein said Piper methysticum plant or processed product thereof is a stem, leaf or root of a Piper methysticum plant or a processed product thereof.
7. The wood preservative according to 6. wherein the processed product is a dry powder or an extract of a stem, leaf or root of Piper methysticum. 
8. The wood preservative according to 1. wherein the compound represented by the formula (I) is a compound represented by Formula (II): 
xe2x80x83wherein R6 is hydroxy or a C1-4 alkoxy, R7 is a hydrogen atom, hydroxy or a C1-4 alkoxy, or R6 and R7 are taken together to form a group represented by xe2x80x94Oxe2x80x94(CH2)nxe2x80x94Oxe2x80x94 wherein n is 1 or 2, R8 is a hydrogen atom or a C1-4 alkoxy, R9 is hydroxy or a C1-4 alkoxy, R17 is a hydrogen atom, hydroxy or a C1-4 alkoxy and X is defined as described above, or a compound represented by Formula (III): 
xe2x80x83wherein R10 is a hydrogen atom, hydroxy or a C1-4 alkoxy, R11 is a hydrogen atom or hydroxy, or R10 and R11 are taken together to form a group represented by xe2x80x94Oxe2x80x94(CH2)nxe2x80x94Oxe2x80x94 wherein n is 1 or 2, R12 is a hydrogen atom or hydroxy, R13 is a C1-4 alkoxy, R18 is a hydrogen atom, hydroxy or a C1-4 alkoxy and X is defined as described above.
9. The wood preservative according to 1. wherein a compound represented by Formula (I) is:
(1) kawain, or kavain
(2) 7,8-dihydrokawain, or 7,8-dihydrokavain
(3) yangonin,
(4) 5,6,7,8-tetrahydroyangonin,
(5) methysticin,
(6) 7,8-dihydromethysticin,
(7) cis-5-hydroxykawain, or cis-5-hydroxykavain
(8) 11-methoxy-12-hydroxy-5,6-dehydrokawain, or 11-methoxy-12-hydroxy-5,6-dehydrokavain
(9) 7,8-dihydroyangonin,
(10) 5,6-dihydroyangonin,
(11) 11-methoxyyangonin,
(12) 10-methoxyyangonin,
(13) 11-hydroxyyangonin or,
(14) 5,6-dehydromethysticin.
10. The wood preservative according to 1. wherein the compound represented by the formula (I) is a compound represented by Formula (IV): 
xe2x80x83wherein each of R14 and R15 is a hydrogen atom or they are taken together to form methylenedioxy, and X is defined as described above.
11. A method for preserving wood which comprises treating wood with an effective amount of a Piper methysticum plant or processed product thereof, or a compound represented by Formula (I). 
xe2x80x83wherein R1, R2, R3, R4 and R16 are same or different and each denotes a hydrogen atom, hydroxy or a C1-4 alkoxy, or R1 and R2 are taken together to form a group represented by xe2x80x94Oxe2x80x94(CH2)nxe2x80x94Oxe2x80x94 wherein n is an integer of 1 to 3, R5 is a C1-4 alkoxy and X is xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94CH2xe2x80x94CH2xe2x80x94 or epoxyethylene, and the bond:

xe2x80x83denotes a single bond or a double bond.
12. Use of a Piper methysticum plant or processed product thereof, or the compound represented by the formula (I) for a production of the wood preservative.